Answer:
2
Explanation:
The Aufbau sequence of increasing energy levels is 1s,2s,2p,3s,3p,4s,3d and so on....
Hope this helps! :D
Find ΔHrxn for the following reaction:
2PbS(s)+3O2(g)→2PbO(s)+2SO2(g)
Answer:
ΔH°rxn = -827.5 kJ
Explanation:
Let's consider the following balanced equation.
2 PbS(s) + 3 O₂(g) → 2 PbO(s) + 2 SO₂(g)
We can calculate the standard enthalpy of reaction (ΔH°rxn) from the standard enthalpies of formation (ΔH°f) using the following expression.
ΔH°rxn = [2 mol × ΔH°f(PbO(s)) + 2 mol × ΔH°f(SO₂(g) )] - [2 mol × ΔH°f(PbS(s)) + 3 mol × ΔH°f(O₂(g) )]
ΔH°rxn = [2 mol × ΔH°f(PbO(s)) + 2 mol × ΔH°f(SO₂(g) )] - [2 mol × ΔH°f(PbS(s)) + 3 mol × ΔH°f(O₂(g) )]
ΔH°rxn = [2 mol × (-217.32 kJ/mol) + 2 mol × (-296.83)] - [2 mol × (-100.4) + 3 mol × 0 kJ/mol]
ΔH°rxn = -827.5 kJ
The standard enthalpy of the reaction is -827.5 kJ/mol
The standard enthalpy of reaction [tex]\mathbf{\Delta H^0_{rxn}}[/tex] is the enthalpy change that happens in a system whenever one mole of the matter is converted through a chemical process under normal conditions.
The given reaction can be expressed as:
2PbS(s) + 3O₂(g) → 2PbO(s) + 2SO₂(g)
The standard enthalpy can be represented by the equation:
[tex]\mathbf{\Delta H^0_{rxn} = \sum \Delta _f ^0(products) - \sum \Delta _f^0(reactants)}[/tex]
At standard conditions, the standard enthalpies of formation of the given species are:
ΔH°f(PbO(s)) = 219 kJ/molΔH°f(SO₂(g)) = -296.83 kJ/molΔH°f(PbS(s)) = 100.4 kJ/molΔH°f(O₂(g)) = 0 kJ/mol
∴
[tex]\mathbf{ \Delta H^0_{rxn} = \Big[2 mol \times \Delta H^0_f(PbO(s)) + 2 mol \times \Delta H^0_ f(SO_2(g) )\Big] - \Big[2 mol \times \Delta H^0_f (PbS(s))} + \mathbf{ 3 mol \times \Delta H^0_f(O_2(g) )\Big] }}[/tex]
[tex]\mathbf{\Delta H^0rxn = [2 mol \times (-217.32 kJ/mol) + 2 mol \times (-296.83)] - [2 mol \times (-100.4)} \\ \mathbf{+ 3 mol \times 0 kJ/mol]}}[/tex]
[tex]\mathbf{\Delta H^0rxn = -827.5 \ kJ/mol}}[/tex]
Therefore, we can conclude that the standard enthalpy of the reaction is -827.5 kJ/mol
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Georgia discovered a piece of metal. She measured its mass as 14 grams and its volume as 2 cm3. Georgia then compared the metal she found with the metals in the table below.
DENSITY OF METALS
Which type of metal did Georgia most likely find?
A.Gold
B.Lead
C.Silver
D.Zinc
Answer:
try dividing the grams and the volume and see what number matches up with your answer
Explanation:What color is the acetic acid plus methyl orange solution and what does this tell you about where the equilibrium is
Answer:
Red
Explanation:
Acetic acid is an acidic medium. Recall that indicators are organic substances whose color changes in response to change in the pH of the solution. often times, the protonated and deprotonated forms of an indicator have different colors.
However, an equilibrium is set up when an indicator is in acid/ basic medium. Methyl orange is red in acid medium and yellow in basic medium.
Hence while in acetic acid, the equilibrium lies towards the protonated form of acetic acid, hence the solution appears red.
Which 2 main body systems work alongside the digestive system?
Which of the following is an example of a chemical change that occurs in your home?
A) Water boiling on the stove
B) Composting your own fertilizer
C) Smashing a window with a baseball
D) Adding food coloring to icing for a cake
empirical formula of N4H8O4
Answer:
NH₂O
Explanation:
Given compound:
N₄H₈O₄
Unknown:
The empirical formula of the compound = ?
Solution:
The empirical formula of a compound is its simplest formula. It expresses the composition of a the compound in the simplest whole ratio of atoms of the different elements present in the compound.
For the given compound:
N₄H₈O₄
Number of moles of N = 4
H = 8
O = 4
the highest common factor is 4 and we simply divide through by this number;
N = 1
H = 2
O = 1
So, the empirical formula of compound is NH₂O
Which of the following statements is true during a solar eclipse?
The moon's light is blocked by the Earth.
The Sun's light is blocked by the Earth.
The Sun's light is blocked from another planet.
The Sun's light is blocked by the Moon.
Answer:
The sun's light is blocked by the moon.
Explanation:
During the eclipse, the moon rotates right in front of the sun, that's why the eclipse is so rare and only happens every four(?) years/
Which statement best describes the octet rule?
A. When an atom becomes an ion, it gains or loses electrons so that its valence shell holds eight electrons.
B. When an atom becomes an ion, it gains or loses protons so that its nucleus holds eight protons.
C. When an atom becomes an ion, it gains or loses eight electrons.
D. When an atom becomes an ion, it gains or loses eight neutrons.
Which of the following best describes the structure of a nucleic acid?
a
Carbon ring(s)
b
Globular or fibrous
c
Single or double helix
d
Hydrocarbon(s)
Mass number is equal to
(10 Points)
O neutrons and electrons
o electrons and protons
O protons and nucleus
protons and neutrons
Help, 8th grade Science
How many molecules of NH3 are produced from 8.01x10-4g of H2
Answer:
1.61 x 10²⁰ molecules
Explanation:
Given parameters:
Mass of the hydrogen gas = 8.01 x 10⁻⁴g
Unknown
Number of molecules of NH₃ = ?
Solution:
Given reaction:
N₂ + 3H₂ → 2NH₃
We have to solve from the known to the unknown
The known specie is the mass of H₂ ;find the number of moles of the specie;
number of moles = [tex]\frac{mass}{molar mass}[/tex]
Molar mass of H₂ = 2(1) = 2g/mol
Number of moles = [tex]\frac{0.0008}{2}[/tex] = 0.0004mol
3 moles of H₂ will produce 2 moles of NH₃0.0004 moles of H₂ will produce [tex]\frac{0.0004 x 2}{3}[/tex] = 0.00027moles of NH₃
1 mole of a substance contains 6.02 x 10²³ molecules
0.00027mole of NH₃ will contain 0.00027 x 6.02 x 10²³
= 1.61 x 10²⁰ molecules
Organisms in overpopulated area do not survive well due to which of the following
Answer:
Reductions in available food and shelter
Explanation:
To solve this we must be knowing each and every concept related to population. Therefore, organisms in over-populated areas do not survive well due to reduction in available food and shelter.
What is population?The group of people from whom a quantitative sample is gathered for a research is referred to as a population. Therefore, a population is any collection of people who have anything in common.
A sample is a representative group of a population chosen at random. This is a smaller group that was selected from the population and possesses all of the population's traits. The observations and inferences drawn from the sample data then applied to the entire population.
Therefore, organisms in over-populated areas do not survive well due to reduction in available food and shelter.
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You have a carbonate buffer with pH 10.3 and a concentration of 2.0 M. What is the buffer capacity of 100 mL of the buffer against 3.0 M CsOH?
Answer:
Explanation:
pH = 10.3
[ H] = 10⁻¹⁰°³
= 5 x 10⁻¹¹ M
concentration of CsOH C = 3 M
pKa of carbonate = 6.35
Ka = 10⁻⁶°³⁵ = 4.46 x 10⁻⁷
Buffer capacity = 2.303 x C x Ka x [ H⁺] / ( Ka + [ H⁺]² )²
= 2.303 x 3 x 4.46 x 10⁻⁷ x 5 x 10⁻¹¹ / ( 4.46 x 10⁻⁷ + 25 x 10⁻²² )²
= 154 x 10⁻¹⁸ / 19.9 x 10⁻¹⁴
= 7.74 x 10⁻⁴ .
Aluminum metal and bromine liquid (red) react violently to make aluminum bromide (white powder). One way to represent this equilibrium is:
Al(s) + 3/2 Br2(l)AlBr3(s)
We could also write this reaction three other ways, listed below. The equilibrium constants for all of the reactions are related. Write the equilibrium constant for each new reaction in terms of K, the equilibrium constant for the reaction above.
1) 2 AlBr3(s) 2 Al(s) + 3 Br2(l)
2) 2 Al(s) + 3 Br2(l) 2 AlBr3(s)
3) AlBr3(s) Al(s) + 3/2 Br2(l)
Answer:
Explanation:
Al(s) + 3/2 Br₂(l) = AlBr₃(s)
K = [ AlBr₃] / [ Al] [ Br₂]³/²
K² = [ AlBr₃]² / [ Al ] ² [ Br₂]³
2 AlBr₃ = 2 Al(s) + 3 Br₂(l) =
K₁ = [ Al ] ² [ Br₂]³ / [ AlBr₃]²
K₁ = ( 1 / K² ) = K⁻²
2 ) 2 Al(s) + 3 Br₂(l) = 2 AlBr₃(s)
K₂ = [ AlBr₃ ]² / [ Al ]² [ Br₂ ]³
K₂ = K²
3 )
AlBr₃(s) = Al(s) + 3/2 Br₂(l)
K₃ = [ Al ] [ Br₂ ] ³/² / [ AlBr₃ ]
= ( 1 / K ) = K⁻¹
Select the reagents you would use to synthesize the compounds below from benzene. Use the minimum number of steps. No more than three steps are required in any synthesis.
a. Br2, FeBr3
b. CH3COCi. AICl3
c. SO3, H2SO4
d. Cl2, FeCl3
e. KMnO4, H2O
f. HNO3, H2SO4
g. Fe, H3O then OH
h. CH3Cl, AICl3
m-chlorobenzenesulfonic acid:
2,4,6-tribromoaniline
Answer:
f and a. That is reagents f[HNO3, H2SO4] is used first then followed by reagent a[Br2, FeBr3]
Explanation:
So, in the production of m-bromonitrobenzene[3-Nitro-1-bromobenzene/1-Bromo-3-nitrobenzene] from benzene from the reagents provided by using the fastest reagents that is to say the reagent with the minimum number of steps, we are going to make use of reagents in option 'f' followed by reagents in option 'a'.
STEP ONE: The first step in the production of m-bromonitrobenzene[3-Nitro-1-bromobenzene/1-Bromo-3-nitrobenzene] from benzene to give the minimum number of steps from the reagents given is nitration by using the reagents in option 'f'' that is HNO3, H2SO4 to give nitrobenzene. The equation for the chemical reaction is given below as:
C₆H₆ + HNO₃, H₂SO₄ -------------------------------------------------------> C6H5NO2.
It is the N⁺O₂ that is been used in the reaction mechanism [from the reaction: HNO₃ + H₂SO₄ < -----------------> N⁺O₂ + HSO₄⁻ + H₂O].
STEP TWO: The next thing to do is to react the nitrobenzene got from the nitration of benzene in step one above with the reagents in option 'a'[Br2, FeBr3]. This step is known as the bromination of nitrobenzene.
C₆H₅NO₂ + Br₂, FeBr3 ------------------------------------------------> C₆H₄BrNO₂.
Which is the best molecule to build collegen, muscle repair, and tendon repair?
a
carohydrates
b
lipids
c
nucleic acids
d
Proteins
Answer:
d
Explanation:
collagen is made of proteins
SOMEONE PLEASE HELP I WILL GIVE BRAINLIEST PLEASEEEEE!!!!!!!!!!
MY ELEMENT IS NICKEL!!
Answer:
Metallurgy can be isolate other elements. Iron and bronze are the common metalsNickel is the metal which reacts with many metalsSome halogen and discredited metalsA certain chemical reaction releases of heat for each gram of reactant consumed. How can you calculate the heat produced by the consumption of of reactant? Set the math up. But don't do any of it. Just leave your answer as a math expression. Also, be sure your answer includes all the correct unit symbols.
Complete Question
The complete question is shown in the first uploaded image
Answer:
So the math expression is
[tex]heat = \frac{ 35. 7 KJ * 1900 \ gram }{ 1 \ gram }[/tex]
Explanation:
From the question we are told that
The heat released for 1 gram of reactant consumed is [tex]H = 37.5 \ KJ/g [/tex]
The mass of reactant considered is [tex]m = 1.9 \ kg = 1900 \ g[/tex]
So if
[tex]37.5 \ KJ [/tex] is produced for 1 gram
Then
x kJ is produced for 1900 g
=> [tex]x = \frac{ 35. 7 KJ * 1900 \ gram }{ 1 \ gram }[/tex]
So the heat released is
[tex]heat = \frac{ 35. 7 KJ * 1900 \ gram }{ 1 \ gram }[/tex]
Alkali metals, such as potassium, must be transported in special sealed containers because they have the ability to burn or explode upon contact with water due to their high reactivity. This is an example of a __________.
Answer:
The Group 1 elements in the periodic table are known as the alkali metals. They include lithium, sodium and potassium, which all react vigorously with water to produce an alkaline solution.
Explanation:
Cathode rays are deflected toward a negatively charged plate in an electric field.
True
False
Answer:
true. cathode rays are deflected
The escape velocity from Earth’s surface is 1.12*10^4 meters per second. At this speed, how many kilometers would a rocket travel in 3 minutes
Answer:
2016 Km.
Explanation:
The following data were obtained from the question:
Speed (S) = 1.12×10⁴ m/s
Time (t) = 3 mins
Distance (d) =.?
Next, we shall convert 3 mins to seconds. This can be obtained as follow:
1 min = 60 s
Therefore,
3 mins = 3 min × 60 s / 1 min
3 mins = 180 s
Next, we shall determine the distance travelled by the rocket. This is illustrated below:
Speed (S) = 1.12×10⁴ m/s
Time (t) = 180 s
Distance (d) =.?
Speed (S) = distance (d) /time (t)
S = d/t
1.12×10⁴ = d/ 180
Cross multiply
d = 1.12×10⁴ × 180
d = 2016000 m
Finally, we shall convert 2016000 m to Km. This can be obtained as shown below:
1000 m = 1 Km
Therefore,
2016000 m = 2016000 m × 1 Km / 1000 m
2016000 m = 2016 Km
Therefore, the rocket will travel 2016 Km in 3 mins
How many moles of H2 are needed to produce 24 moles of NH3?
Answer:
36 mol of H2
Explanation:
The balanced equation of the reaction is given as;
3H2 + N2 --> 2NH3
From the reaction;
It takes 3 mol of H2 reacting with 1 mol of N2 to form 2 mol of NH3
3 mol of H2 = 2 mol of NH3
x mol of H2 = 24 mol of NH3
x = (24 * 3) / 2 = 36 mol of H2
Carbonic acid, H2CO3, has two acidic hydrogens. A solution containing an unknown concentration of carbonic acid is titrated with potassium hydroxide. It requires 22.9 mL of 1.430 M KOH solution to titrate both acidic protons in 54.2 mL of the carbonic acid solution.
Required:
a. Write a balanced net ionic equation for the neutralization reaction. Include physical states.
b. Calculate the molarity of the carbonic acid solution.
Answer:
a. H₂CO₃(aq) + KOH(aq) ⇄ K₂CO₃(aq) + H₂O(l)
b. 0.603 M
Explanation:
Step 1: Write the neutralization reaction
H₂CO₃(aq) + KOH(aq) ⇄ K₂CO₃(aq) + H₂O(l)
Step 2: Calculate the reacting moles of KOH
22.9 mL of 1.430 M KOH react.
0.0229 L × (1.430 mol/L) = 0.0327 mol
Step 3: Calculate the reacting moles of H₂CO₃
The molar ratio of H₂CO₃ to KOH is 1:1. The reacting moles of H₂CO₃ are 1/1 × 0.0327 mol = 0.0327 mol.
Step 4: Calculate the molarity of H₂CO₃
0.0327 moles of H₂CO₃ are in a volume of 54.2 mL. The molarity of H₂CO₃ is:
M = 0.0327 mol/0.0542 L = 0.603 M
A plant uses carbon dioxide and water to form food and oxygen. Why is this a chemical change?
Answer:
The plant uses carbon dioxide and water to make an entirely new chemical hence chemical change.
Explanation:
Plants create their own 'food', they turn carbon dioxide water and sunlight to create starch and glucose..
Answer:
The properties of carbon dioxide and oxygen are different.
Explanation:
im taking the exam right now and Im pretty sure it's D The properties of carbon dioxide and oxygen are different.
For which of the following processes would S° be expected to be most positive? a) O2(g) + 2H2(g) 2H2O(g) b) H2O(l) H2O(s) c) NH3(g) + HCl(g) NH4Cl(g) d) 2NH4NO3(s) 2N2(g) + O2(g) + 4H2O(g) e) N2O4(g) 2NO2(g) 12. Which of the following statements is
Answer:
Explanation:
a) O₂(g) + 2H₂(g) = 2H₂O
b) H₂O(l) = H₂O(s)
c) NH₃(g) + HCl(g) = NH₄Cl(g)
d) 2NH₄NO₃(s) = 2N₂(g) + O₂(g) + 4H₂O(g)
e) N₂O₄(g) = 2NO₂(g)
ΔS is positive when there is increase in disorderliness. It happens when there is increase in volume .
Increase is volume is maximus in the following reaction.
d) 2NH₄NO₃(s) = 2N₂(g) + O₂(g) + 4H₂O(g)
in this reaction solid NH₄NO₃ is changed to 7 x 22.4 L of gases so there is maximum increase in volume . Hence maximum increase in entropy . Hence ΔS is most positive .
Which of the following compounds contains polar covalent bonds?
a) CS2
b) LiF
c) F2
d) CH3F
Answer:
no d
Explanation:
it has a permanent dipole
CH₃F compound contains polar covalent bonds in its structure, hence option D is correct.
This happens when the electronegativity of the relevant atoms differs significantly.
The electronegativities of the carbon and fluorine atoms in CH3F are dissimilar. Because fluorine is more electronegative than carbon, it attracts the shared electrons to it, giving the fluorine atom a partial negative charge and the carbon atom a partial positive charge.
A polar covalent bond is created as a result of this unequal charge distribution. CH₃F compound contains polar covalent bonds in its structure.
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Which two chemical formulas represent molecules?
Answer:
There are three basic types of chemical formula, the empirical formula, the molecular formula, and the structural formula.
A sample of methane gas is collected at 285 K and cooled to 245 K. At 245 K the volume of the gas is 75.0 L. Calculate the volume of the methane gas at 285 K. Assume constant pressure
Answer:
V₂ = 87.24 L
Explanation:
Charle's law states that at constant pressure, the volume of the gas is directly proportional to the temperature. Its mathematical form is given by :
[tex]\dfrac{V_1}{T_1}=\dfrac{V_2}{T_2}[/tex]
We have, V₁ = 75, T₁ = 245 K, T₂ = 285, V₂ = ?
Putting all the values, we get :
[tex]V_2=\dfrac{V_1T_2}{T_1}\\\\V_2=\dfrac{75\times 285}{245}\\\\V_2=87.24\ L[/tex]
So, the new volume is 87.24 L.
Which profile best shows the topography alone line AD